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Help w/tach....

Discussion in 'The Garage' started by conoverbandit, Mar 15, 2005.

  1. conoverbandit

    conoverbandit 1/2 ton status

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    Hey y'all,

    I got a factory tach cluster that came with my truck, the guy said it "worked" but I'm sure it's not the right cluster pack for this truck as orginally it was 6cyl. 2 by truck. Everything works except the "temp" gauge, which quivers when the ignition is turned all the way over in the "start" posistion. Also the tach works, but not right.Someone suggested I needed a resistor in between the hot side of the coil and the tach? anyone got an idea on this? I hooked it up and it works, but will not increase as engine rpm does. I turned the wires areound and it was like at idle it was showing like 5 grand, and if you rev it it wil go all the way back around to like 4-5 and stay there. Maybe it's messed up? anyone got any ideas? Thanks,
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    6cyl tachs don't work on 8's. 25% more firings per revolution means 25% higher readings if it's on an 8.

    Some applications had a switch on the tach printed circuit board for 6/8 cylinders, but I haven't seen that on the truck tachs. I've heard of someone "fixing" the 6/8 issue, but can't recall where I saw it. Perhaps search google...I know it was regarding a fiero, and I'm sure it was because they put an 8 in place of the 6 that was there from the factory.
     
  3. conoverbandit

    conoverbandit 1/2 ton status

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    Ok,

    Let me clarify if I can. The truck was orginal 6cyl. That I know of it still has the orginal wiring harness. The truck now has a 8 cyl, and I don't think this is the right cluster for this truck. In other words it's an "add-on" someone put in the truck.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    What kind of tach?

    The 4/6/8 issue is handled in the printed circuit board of the tach itself. If it's an aftermarket tach, or some other application, perhaps it is already set up for 8 cylinder, or is "universal". Thus the tach wiring doesn't really matter...I've seen different pins used, but for GM HEI (all that I've seen) tachs require 12V ignition, ground, and a distributor signal, thats it.

    Hope that helps out somehow.
     

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